Use a single views::MenuConfig instance for each platform

ui/views/controls/menu/menu_config.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/menu/menu_config.h"
 
-#include "build/build_config.h"
+#include "base/macros.h"
 
 namespace views {
 
-MenuConfig::MenuConfig(const ui::NativeTheme* theme)
+MenuConfig::MenuConfig()
     : arrow_color(SK_ColorBLACK),
       menu_vertical_border_size(3),

[Evan Stade, 2015/12/07 19:51:42]

I think it's fairly confusing to have this common initializer block. It's nigh
impossible to tell which parts of this actually matter to which platforms. Can
we move this to each platform file and only set the defaults that actually
matter (i.e. aren't overridden in init)?

You/someone could also do this as a follow-up if you don't want to make it part
of this CL.

[tapted, 2015/12/08 11:49:23]

I think a follow-up is best - since it will need a bit of scrutiny to ensure the
values are moved over correctly.

There might be some nicer things to try too, like `bzero`ing the struct in the
constructor, or using a static initializer once the FontList is moved out.

       menu_horizontal_border_size(0),
       submenu_horizontal_inset(3),
       item_top_margin(4),
       item_bottom_margin(3),
       item_no_icon_top_margin(4),
       item_no_icon_bottom_margin(4),
       item_left_margin(10),
       label_to_arrow_padding(10),
       arrow_to_edge_padding(5),
       icon_to_label_padding(10),
@@ skipping 11 matching lines @@
       item_min_height(0),
       show_accelerators(true),
       always_use_icon_to_label_padding(false),
       align_arrow_and_shortcut(false),
       offset_context_menus(false),
       use_outer_border(true),
       icons_in_label(false),
       check_selected_combobox_item(false),
       show_delay(400),
       corner_radius(0) {
-  Init(theme);
+  Init();
 }
 
 MenuConfig::~MenuConfig() {}
 
+// static
+const MenuConfig& MenuConfig::instance() {
+  CR_DEFINE_STATIC_LOCAL(MenuConfig, instance, ());
+  return instance;
+}
+
 }  // namespace views